IPv4 / IPv6 CIDR calculator

Enter an address and prefix length to see the network block and usable range. Math is local.

Confirm with your cloud console before you punch a security-group hole.

How to Use

  1. Paste 10.0.0.0/24 or an IPv6 prefix.
  2. Read network, mask, and host count.
  3. Copy the range into a ticket or Terraform comment.
  4. Do not assume the calculator updated your VPC.

Key Features

  • IPv4 and IPv6 prefixes
  • Local arithmetic
  • No account
  • Pairs with IP lookup

Frequently Asked Questions

Does this change my firewall?

No.

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